It is desirable in both military and civilian settings to protect boundaries. In particular, it is desirable for security to be notified when intruders cross boundaries. For example, intruder detection is important in a military “safe zone” or to detect gate crashers in events such as music festivals and open air concerts.
One type of trigger mechanism used in military applications uses a trip wire under tension. Release of the tension in the trip wire causes activation in the trigger mechanism, for example by pulling out a pin in the mechanism. A disadvantage of this known type of trigger mechanism is that the use of trip wire under tension enables detection.